Liquid crystal display device and method of manufacturing the same

ABSTRACT

In a liquid crystal display device of an IPS system, to realize reduction of manufacturing cost and improvement of yield by decreasing the number of steps for manufacturing a TFT. A channel etch type bottom gate TFT structure, where patterning of a source region and a drain region and patterning of a source wiring and a pixel electrode are carried out by the same photomask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an active matrix type liquid crystaldisplay device, and particularly to an active matrix type liquid crystaldisplay device of an IPS (In-Plane Switching) system (=transverseelectric field system).

2. Description of Related Art

An active matrix type liquid crystal display device using an activeelement such as a thin film transistor (TFT) is known. The active matrixtype liquid crystal display device can increase pixel density, is smalland lightweight, and consumes less power, so that as a substitute for aCRT, a product such as a monitor of a personal computer or a liquidcrystal television has been developed. Especially, a technique offorming an active layer of a TFT by a crystalline semiconductor filmtypified by polycrystalline silicon makes it possible to form a drivercircuit as well as a switching TFT for a pixel portion (hereinafterreferred to as a pixel TFT) on the same substrate, and is ranked as atechnique to contribute to miniaturization and weight lightening of aliquid crystal display device.

In the liquid crystal display device, a liquid crystal is sealed betweena pair of substrates, and liquid crystal molecules are oriented by anelectric field which is applied between a pixel electrode (individualelectrode) of one of the substrates and an opposite electrode (commonelectrode) of the other substrate and is approximately vertical to asubstrate plane. However, such a driving method of a liquid crystal hasa defect that an angle of view is narrow, that is, although a normaldisplay state is obtained when it is viewed in a direction vertical tothe substrate plane, a color tone is changed and becomes unclear when itis viewed in an oblique direction.

As a method of overcoming this defect, there is an IPS system. Thissystem has a feature that both a pixel electrode and a common wiring areformed on one of substrates and an electric field is changed to atransverse direction, and liquid crystal molecules do not rise but theirorientation is controlled in the direction almost parallel with asubstrate plane. By this operation principle, the angle of view can bewidened.

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

Usage of a liquid crystal display device has been widened, and also inthe IPS system, with enlargement of a screen size, a demand for highfineness, high aperture ratio, and high reliability has increased. Atthe same time, a demand for improvement of productivity and reduction ofcost has also increased.

In order to improve the productivity and to improve yield, the reductionin the number of steps is considered as an effective means.

Specifically, it is necessary to reduce the number of photomasks neededto produce the TFT. The photomask is used in a photolithographytechnique in order to form a photoresist pattern, which becomes anetching process mask, on the substrate.

By using one photomask, there are applied with steps such as applyingresist, pre-baking, exposure, development, and post-baking, and steps offilm deposition and etching before and after, and in addition, resistpeeling, cleaning, and drying steps are added. Therefore, the entireprocess becomes complex, which leads to a problem.

Further, static electricity is generated by causes such as frictionduring manufacturing steps because the substrate is an insulator. Ifstatic electricity is generated, then short circuits develop at anintersection portion of wirings formed on the substrate, anddeterioration or breakage of the TFT due to static electricity leads todisplay faults or deterioration of image quality in electro-opticaldevices. In particular, static electricity develops during rubbing inthe liquid crystal orienting process performed in the manufacturingsteps, and this becomes a problem.

The present invention is for answering these types of problems, and anobject of the present invention is to reduce the number of steps formanufacturing a TFT, and to realize a reduction in the production costand an improvement in a liquid crystal display device of an IPS system.

Further, an object of the present invention is to provide a structureand a method of manufacturing the structure for resolving the problemsof damage to the TFT and deterioration of TFT characteristics due tostatic electricity.

Means for Solving the Problem

In order to solve the above problems, the present invention ischaracterized by employing a channel etch type bottom gate TFTstructure, and by performing patterning of a source region, a drainregion, and patterning of a source wiring, a pixel electrode by usingthe same photomask.

A method of manufacturing of the present invention is simply explainedbelow.

First, a gate wiring 102 and a common wiring 103 a (and a commonelectrode 103 b) are formed using a first mask (photomask number 1).

Next, an insulating film (gate insulating film) 104 a, a first amorphoussemiconductor film 105, a second amorphous semiconductor film 106containing an impurity element which imparts n-type conductivity, and afirst conductive film 107 are laminated in order. (FIG. 2(A)) Note thata microcrystalline semiconductor film may be used as a substitute forthe amorphous semiconductor film, and that a microcrystallinesemiconductor film containing an impurity element which imparts n-typeconductivity may be used as a substitute for the amorphous semiconductorfilm containing an impurity element which imparts n-type conductivity.In addition, these films (104 a, 105, 106, and 107) can be formed insuccession without exposure to the atmosphere in a plurality ofchambers, or in the same chamber, using sputtering or plasma CVD. Themixing in of impurities can be prevented by having no exposure to theatmosphere.

Next, by using a second mask (photomask number 2): the above firstconductive film 107 is patterned, forming a wiring (which later becomesa source wiring and a pixel electrode) 114 from the first conductivefilm; the above second amorphous semiconductor film 106 is patterned,forming a second amorphous semiconductor film 112 containing an impurityelement which imparts n-type conductivity; and the above first amorphoussemiconductor film 105 is patterned, forming a first amorphoussemiconductor film 110. (FIG. 2(B))

Thereafter, a second conductive film 116 is formed on the entire surface(FIG. 2(D)). Note that as the second conductive film 116, a transparentconductive film may be used, or a conductive film having reflectivitymay be used. This second conductive film is provided for prevention ofelectro-static damage, protection of a wiring, and electrical connectionof a terminal portion.

Next, by using a third mask (photomask number 3): the above secondconductive film 116 is patterned; the above wiring 114 is patterned,forming a source wiring 121 and a pixel electrode 122; the secondamorphous semiconductor film 112 containing an impurity element whichimparts n-type conductivity is patterned, forming a source region 119and a drain region 120 from the second amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity; and aportion of the above first amorphous semiconductor film 110 is removed,forming a first amorphous semiconductor film 118. (FIG. 3(A))

By using this type of constitution, the number of photomasks used in thephotolithography technique can be set to 3 when manufacturing a pixelTFT portion.

A structure of the present invention disclosed in this specification is:

a liquid crystal display device including a pair of substrates and aliquid crystal held between the pair of substrates, wherein the liquidcrystal display device is characterized in that

the gate wiring 102 and the common electrode 103 b is formed on one ofthe pair of substrates,

the insulating film 104 b is formed on the gate wiring 102 and thecommon electrode 103 b,

the amorphous semiconductor film 118 is formed on the insulating film,

the source region 119 and the drain region 120 are formed on theamorphous semiconductor film,

the source wiring 121 or the pixel electrode 122 is formed on the sourceregion 119 or the drain region 120,

the pixel electrode 122 and the common electrode 103 b are disposed sothat an electric field parallel with a substrate plane of the onesubstrate is generated, and

one end face of the drain region 120 or the source region 119 issubstantially coincident with an end face of the amorphous semiconductorfilm 118 and an end face of the pixel electrode 122.

Further, another structure of the present invention is:

a liquid crystal display device including a pair of substrates and aliquid crystal held between the pair of substrates, wherein the liquidcrystal display device is characterized in that

the gate wiring 102 and the common electrode 103 b are formed on one ofthe pair of substrates,

the insulating film 104 b is formed on the gate wiring 102 and thecommon electrode 103 b,

the amorphous semiconductor film 118 is formed on the insulating film,

the source region 119 and the drain region 120 are formed on theamorphous semiconductor film 118,

the source wiring 121 or the pixel electrode 122 is formed on the sourceregion 119 or the drain region 120,

the pixel electrode 122 and the common electrode 103 b are disposed sothat an electric field parallel with a substrate plane of the onesubstrate is generated, and

one end face of the drain region 120 or the source region 119 issubstantially coincident with an end face of the amorphous semiconductorfilm 118 and an end face of the pixel electrode 122, and the other endface is substantially coincident with an end face of the source wiring122.

Further, another structure of the present invention is:

a liquid crystal display device including a pair of substrates and aliquid crystal held between the pair of substrates, wherein the liquidcrystal display device is characterized in that

the gate wiring 102 and the common electrode 103 b is formed on one ofthe pair of substrates,

the insulating film is formed on the gate wiring 102 and the commonelectrode 103 b,

the amorphous semiconductor film 118 is formed on the insulating film,

the source region 119 and the drain region 120 are formed on theamorphous semiconductor film,

the source wiring 121 or the pixel electrode 122 is formed on the sourceregion 119 or the drain region 120,

the pixel electrode 122 and the common electrode 103 b are disposed sothat an electric field parallel with a substrate plane of the onesubstrate is generated, and

the amorphous semiconductor film 118 and an amorphous semiconductor filmcontaining an impurity element which imparts an n-type conductivity arelaminated under the source wiring.

Further, in the above-mentioned respective structures, the liquidcrystal display device is characterized in that the source region andthe drain region is made from an amorphous semiconductor film containingan impurity element which imparts n-type conductivity.

Further, in the above-mentioned respective structures, the liquidcrystal display device is characterized in that the gate wiring 102 isformed from a film of an element selected from the group consisting ofAl, Cu, Ti, Mo, W, Ta, Nd, and Cr, from an alloy film of said elements,or from a lamination film of said elements.

Still further, in the above-mentioned respective structures, the liquidcrystal display device is characterized in that the source region 119and the drain region 120 are formed by using the same mask as that ofthe pixel electrode 122. Moreover, it is characterized in that thesource region 119 and the drain region 120 are formed by using the samemask as that of the source wiring 121.

Yet further, in the above-mentioned respective structures, the liquidcrystal display device is characterized in that in the amorphoussemiconductor film, its thickness in a region where it is in contactwith the source region and the drain region is thicker than itsthickness in a region between the region where it is in contact with thesource region and the region where it is in contact with the drainregion.

Yet further, in the above-mentioned respective structures, the liquidcrystal display device is characterized in the pixel electrode iscovered with a transparent conductive film. Besides, it is characterizedin that the source wiring and a terminal on an extension of the sourcewiring are covered with a transparent conductive film.

Further, a structure of the invention to attain the above-mentionedrespective structures is a method of manufacturing a liquid crystaldisplay device, characterized in that the method comprises:

a first step of forming the gate wiring 102 and the common electrode 103b (and the common wiring 103 a) on an insulating surface by using afirst mask;

a second step of forming the insulating film 104 a covering said gatewiring 102 and said common electrode 103 b;

a third step of forming the first amorphous semiconductor film 105 onsaid insulating film 104 a;

a fourth step of forming the second amorphous semiconductor film 106,containing an impurity element which imparts n-type conductivity, onsaid first amorphous semiconductor film 105;

a fifth step of forming the first conductive film 107 on said secondamorphous semiconductor film 106;

a sixth step of patterning said first amorphous semiconductor film 105by using a second mask; of patterning said second amorphoussemiconductor film 106 by using said second mask; of patterning saidfirst conductive film 107 by using said second mask; and of forming thewiring 114 from said first conductive film; and

an eighth step of patterning said wiring 114 by using said third mask,forming the source wiring 121 and the pixel electrode 122; of patterningsaid second amorphous semiconductor film 112 by using said third mask,forming the source region 119 and the drain region 120 made from saidsecond amorphous semiconductor film; and of performing removal of aportion of said first amorphous semiconductor film by using said thirdmask.

Still further, another structure of the present invention to attain theabove-mentioned respective structures is a method of manufacturing aliquid crystal display device characterized in that the methodcomprises:

a first step of forming the gate wiring 102 and the common electrode 103b (and the common wiring 103 a) on the insulating surface by using afirst mask;

a second step of forming the insulating film 104 a covering said gatewiring 102 and said common electrode 103 b;

a third step of forming the first amorphous semiconductor film 105 onsaid insulating film 104 a;

a fourth step of forming the second amorphous semiconductor film 106,containing an impurity element which imparts n-type conductivity, onsaid first amorphous semiconductor film;

a fifth step of forming the first conductive film 107 on said secondamorphous semiconductor film 106;

a sixth step of patterning said first amorphous semiconductor film 105by using a second mask; of patterning said second amorphoussemiconductor film 106 by using said second mask; of patterning saidfirst conductive film 107 by using said second mask; and of forming thewiring 114 from said first conductive film;

a seventh step of forming the second conductive film 116 contacting andoverlapping said wiring 114; and

an eighth step of patterning said second conductive film 116 by using athird mask, forming an electrode made from said second conductive film;of patterning said wiring 114 by using said third mask, forming thesource wiring 121 and the pixel electrode 122; of patterning said secondamorphous semiconductor film 116 by using said third mask, forming thesource region 119 and the drain region 120 made from said secondamorphous semiconductor film; and of performing removal of a portion ofsaid first amorphous semiconductor film by using said third mask.

In the above structure, it is characterized in that the secondconductive film 116 is a transparent conductive film.

Further, in the above-mentioned respective structures, it ischaracterized in that the pixel electrode and the common electrode aredisposed so that an electric field parallel with the insulating surfaceis generated.

Effect of the Invention

With the present invention, an electro-optical device of an IPS systemprepared with a pixel TFT portion, having a reverse stagger typen-channel TFT, and a storage capacitor can be realized through threephotolithography processes using three photomasks.

Further, when forming a protecting film, an electro-optical device of anIPS system prepared with a pixel TFT portion, having a reverse staggertype n-channel TFT protected by an inorganic insulating film, and astorage capacitor can be realized through four photolithographyprocesses using four photomasks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a top view of the present invention.

FIGS. 2A-D are cross-sectional views showing a process of manufacturingan active matrix substrate.

FIGS. 3A-C are cross-sectional views showing the process ofmanufacturing the active matrix substrate.

FIG. 4 is a top view showing the process of manufacturing the activematrix substrate.

FIG. 5 is a top view showing the process of manufacturing the activematrix substrate.

FIG. 6 is a cross-sectional view of a liquid crystal display device.

FIG. 7 is a top view for explaining the arrangement of a pixel portionand an input terminal portion of a liquid crystal display device.

FIG. 8 is a cross-sectional view showing an implemented structure of aliquid crystal display device.

FIGS. 9A-B are top views and a cross-sectional views of an inputterminal portion.

FIG. 10 is a top view of a manufacturing device.

FIG. 11 is a top view of a manufacturing device.

FIG. 12 is a diagram showing an implementation of a liquid crystaldisplay device.

FIGS. 13A-B are cross-sectional views showing an implementationstructure of a liquid crystal display device.

FIG. 14 is a cross-sectional view showing an implemented structure of aliquid crystal display device.

FIG. 15 is a diagram showing a top view of the invention

FIGS. 16A-B are a top view and a circuit diagram of a protectingcircuit.

FIGS. 17A-E are diagrams showing examples of electronic equipment.

FIGS. 18A-C are diagrams showing examples of electronic equipment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment modes of the present invention will be described below.

FIG. 1 is an example of a plan view showing a pixel structure of an IPSsystem in the present invention, and here, for simplification, one pixelstructure in a plurality of pixels arranged in matrix form is shown.FIG. 2 and FIG. 3 are views showing manufacturing steps.

As shown in FIG. 1, this active matrix substrate includes a plurality ofgate wirings arranged in parallel with each other and a plurality ofsource wirings perpendicular to the respective gate wirings. Besides, itincludes a plurality of common wirings in the same layer as the gatewirings.

Besides, a pixel electrode 122 is disposed in a region surrounded by thegate wirings 102 and the source wirings 121. Besides, two commonelectrodes 103 b parallel to each other are disposed at both sides ofthis pixel electrode 122. A liquid crystal is driven by using anelectric field in a transverse direction formed between this pixelelectrode 122 and the common electrodes 103 b. Besides, in order todecrease a light leakage due to a gap between the common electrode andthe source wiring, they may be disposed to partially overlap with eachother.

Further, a TFT is formed in the vicinity of an intersection portion ofthe gate wirings 102 and the source wirings 121 as a switching element.This TFT is a reverse stagger type TFT (channel etch type) having achannel forming region formed from a semiconductor film possessing anamorphous structure (hereafter referred to as a first amorphoussemiconductor film).

Further, the TFT is formed by a lamination of, in order on an insulatingsubstrate, a gate electrode (formed integrally to the gate wiring 102),a gate insulating film, a first amorphous semiconductor film, a sourceregion or a drain region made from a second amorphous semiconductorfilm, containing a impurity element which imparts n-type conductivity, asource electrode (formed as integrated with the source wirings 121) anda pixel electrode 122.

Further, the film thickness of a region between a region contacting thesource region and a region contacting the drain region is thinnercompared to other regions of the first amorphous semiconductor film. Thereason that the film thickness becomes thin is that when forming thesource region and the drain region by partitioning the second amorphoussemiconductor film, which contains the impurity element for impartingn-type conductivity, by etching, a portion of the first amorphoussemiconductor film is also removed. Further, an end surface of the pixelelectrode, and an end surface of the drain region coincide by thisetching process. This type of reverse stagger type TFT is referred to asa channel etched type TFT. Furthermore, the end surface of the sourceregion, and the end surface of the source wiring coincide.

Further, under the source wirings (including the source electrode) andthe pixel electrode 122, a gate insulating film, a first amorphoussemiconductor film, and a second amorphous semiconductor film containingan impurity element which imparts n-type conductivity are laminated inorder on the insulating substrate.

Besides, a storage capacitance is formed of the common wiring 103 a, thepixel electrode 122 (or the second amorphous semiconductor filmcontaining the impurity element which imparts the n-type conductivity,the first amorphous semiconductor film), and an insulating film 104 bexisting therebetween.

A second conductive film 124 made of a transparent electrode and beingin contact with the source wiring, and a second conductive film 123 madeof a transparent electrode and being in contact with the pixel electrodeserve to prevent static electricity generated in a subsequentmanufacturing step, especially in a rubbing processing. Besides, thissecond conductive film 124 facilitates electrical connection whenconnection with an FPC is made at a terminal portion.

Besides, although the IPS system is normally a transmission type, it isalso possible to make a reflection type display device if a metalsubstrate or an insulating substrate on which a dielectric multi-layerfilm is formed is used as an opposite substrate and a substrate intervalis made half of that of the transmission type.

An explanation of the present invention having the above structure isperformed in more detail by the embodiments shown below.

EMBODIMENTS Embodiment 1

An embodiment of the invention is explained using FIGS. 1 to 7. ThisEmbodiment shows a method of manufacturing a liquid crystal displaydevice, and a detailed explanation of a method of forming a TFT of apixel portion on a substrate by a reverse stagger type TFT (channeletching type), and manufacturing a storage capacitor connected to theTFT, is made in accordance with the processes used. Further, amanufacturing process for a terminal section, formed in an edge portionof the substrate, and for electrically connecting to wirings of circuitsformed on other substrates, is shown at the same time in the samefigures.

In FIG. 2(A), a glass substrate, comprising such as barium borosilicateglass or aluminum borosilicate glass, typically Corning Corp. #7059glass or #1737 glass, can be used as a substrate 100 havingtranslucency. In addition, a translucent substrate such as a quartzsubstrate or a plastic substrate can also be used.

Next, after forming a conductive layer on the entire surface of thesubstrate, a first photolithography process is performed, a resist maskis formed, unnecessary portions are removed by etching, and wirings andelectrodes (the gate wiring 102 including a gate electrode, a commonwiring 103 a including a common electrode 103 b and a terminal 101) areformed. Etching is performed at this time to form a tapered portion inat least an edge portion of the gate electrode 102. A top view of thisstage is shown in FIG. 4.

It is preferable to form the gate wiring 102 including the gateelectrode, the common wiring 103 a, and the terminal 101 of the terminalportion from a low resistivity conductive material such as aluminum(Al), copper (Cu) or the like, but simple Al has problems such asinferior heat resistance and easily corrodes, and therefore it iscombined with a heat resistant conductive material. Further, AgPdCualloy may be used as the low resistivity conductive material. Oneelement selected from the group consisting of titanium (Ti), tantalum(Ta), tungsten (W), molybdenum (Mo), chromium (Cr), Neodymium (Nd), oran alloy comprising the above elements, or an alloy film of acombination of the above element, or a nitrated compound comprising theabove element is formed as the heat resistant conductive material. Forexample, a lamination of Ti and Cu or a lamination of TaN and Cu can begiven. Furthermore, forming in combination with a heat resistantconductive material such as Ti, Si, Cr, or Nd, etc., it is preferablebecause of improved levelness. Further, only such heat resistantconductive film may also be formed, for example, in combination with Moand W.

In realizing the liquid crystal display device, it is preferable to formthe gate electrode and the gate wiring by a combination of a heatresistant conductive material and a low resistivity conductive material.An appropriate combination in this case is explained.

Provided that the screen size is on the order of, or less than 5 inchdiagonal type, a two layer structure of a lamination of a conductivelayer (A) made from a nitride compound of a heat resistant conductivematerial, and a conductive layer (B) made from a heat resistantconductive material is used. The conductive layer (B) may be formed froman element selected from the group consisting of Al, Cu, Ta, Ti, W, Nd,and Cr, or from an alloy of the above elements, or from an alloy film ofa combination of the above elements, and the conductive layer (A) isformed from a film such as a tantalum nitride (TaN) film, a tungstennitride (WN) film, or a titanium nitride (TiN) film. For example, it ispreferable to use a double layer structure of a lamination of Cr as theconductive layer (A) and Al containing Nd as the conductive layer (B).The conductive layer (A) is given a thickness of 10 to 100 nm(preferably between 20 and 50 nm), and the conductive layer (B) is madewith a thickness of 200 to 400 nm (preferably between 250 and 350 nm).

On the other hand, in order to be applied to a large screen, it ispreferable to use a three layer structure of a lamination of aconductive layer (A) made from a heat resistant conductive material, aconductive layer (B) made from a low resistivity conductive material,and a conductive layer (C) made from a heat resistant conductivematerial. The conductive layer (B) made from the low resistivityconductive material is formed from a material comprising aluminum (Al),and in addition to pure Al, Al containing between 0.01 and 5 atomic % ofan element such as scandium (Sc), Ti, Nd, or silicon (Si), etc. is used.The conductive layer (C) is effective in preventing generation ofhillocks in the Al of the conductive layer (B). The conductive layer (A)is given a thickness of 10 to 100 nm (preferably between 20 and 50 nm),the conductive layer (B) is made from 200 to 400 nm thick (preferablebetween 250 and 350 nm), and the conductive layer (C) is from 10 to 100nm thick (preferably between 20 and 50 nm). In Embodiment 1, theconductive layer (A) is formed from a Ti film with a thickness of 50 nm,made by sputtering with a Ti target, the conductive layer (B) is formedfrom an Al film with a thickness of 200 nm, made by sputtering with anAl target, and the conductive layer (C) is formed from a 50 nm thick Tifilm, made by sputtering with a Ti target.

An insulating film 104 a is formed next on the entire surface. Theinsulating film 104 a is formed using sputtering, and has a filmthickness of 50 to 200 nm.

For example, a silicon nitride film is used as the insulating film 104a, and formed to a thickness of 150 nm. Of course, the gate insulatingfilm is not limited to this type of silicon nitride film, and anotherinsulating film such as a silicon oxide film, a silicon oxynitride film,or a tantalum oxide film may also be used, and the gate insulating filmmay be formed from a single layer or a lamination structure made fromthese materials. For example, a lamination structure having a siliconnitride film as a lower layer and a silicon oxide film as an upper layermay be used.

Next, a first amorphous semiconductor film 105 is formed with athickness of 50 to 200 nm (preferably between 100 and 150 nm) on theinsulating film 104 a over the entire surface by using a known methodsuch as plasma CVD or sputtering (not shown in the figure). Typically,an amorphous silicon (a-Si) film is formed with a thickness of 100 nm bysputtering using a silicon target. In addition, it is also possible toapply a microcrystalline semiconductor film, or a compound semiconductorfilm having an amorphous structure, such as an amorphous silicongermanium film (Si_(x)Ge_((1-x)), (0<x<1)) and amorphous silicon carbide(Si_(x)C_(y)), etc., for the first amorphous semiconductor film.

A second amorphous semiconductor film containing an impurity elementimparting one conductivity type (n-type or p-type) is formed next with athickness of 20 to 80 nm. The second amorphous semiconductor filmcontaining an impurity element imparting one conductivity type (n-typeor p-type) is formed on the entire surface by a known method such asplasma CVD or sputtering. In this Embodiment the second amorphoussemiconductor film 106 containing n-type impurity element is depositedby using a silicon target added with phosphorus (P). Alternatively, thesecond amorphous semiconductor film containing an impurity elementimparting n-type may also be formed from a hydrogenated microcrystallinesilicon film (pc-Si:H).

Next, a first conductive film 107 which comprises a metallic material isformed by sputtering or vacuum evaporation. There are no particularlimitation on the material of the first conductive film 107 providedthat the material is a metallic material which can form ohmic contactwith the second amorphous semiconductor film 106, and an elementselected from the group consisting of Al, Cr, Ta, and Ti, or an alloycomprising the above elements, and an alloy film of a combination of theabove elements or the like can be given. Sputtering is used in thisEmbodiment to form a Ti film having 50 to 150 nm thickness, an aluminum(Al) having 300 to 400 nm thickness piled on the Ti film and further onthe Al film a Ti film having 100 to 150 nm are formed as the firstconductive film 107. (FIG. 2(A))

The insulating film 104 a, the first amorphous semiconductor film 105,the second amorphous semiconductor film 106 containing an impurityelement which imparts n-type, and the first conductive film 107 are allmanufactured by a known method, and can be manufactured by plasma CVD orsputtering. The films (104 a, 105, 106 and 107) are formed in successionby sputtering, and suitably changing the target or the sputtering gas inEmbodiment 1. The same reaction chamber, or a plurality of reactionchambers, in the sputtering apparatus is used at this time, and it ispreferable to laminate these films in succession without exposure to theatmosphere. By thus not exposing the films to the atmosphere, the mixingin of impurities can be prevented.

Next, a second photolithography process is performed, a resist masks 108and 109 are formed, and by removing unnecessary portions by etching, awiring (which forms a source wiring and a pixel electrode in the laterstep) is formed. Wet etching or dry etching is used as the etchingprocess at this time. The first amorphous semiconductor film 105, thesecond amorphous semiconductor film 106 containing an impurity elementimparting n-type and the conductive metal film 107 are etched, and afirst amorphous semiconductor film 110, a second amorphous semiconductorfilm containing an impurity element imparting n-type 112 and aconductive metal film 114 are formed in the pixel TFT portion.Accordingly the edge surface of the films approximately coincide.Further in the capacitor portion a first amorphous semiconductor film111, a second amorphous semiconductor film 113 containing an impurityelement imparting n-type and a conductive metal film 115 are formed.Similarly, the edge surface of these films coincide. The firstconductive film 107 formed by laminating a Ti film, an Al film and a Tifilm in order is etched by dry etching using reaction gas of mixed gasof SiCl₄, Cl₂ and BCl₃ and the first amorphous semiconductor film 105and the second amorphous semiconductor film 106 containing an impurityelement which imparts n-type are selectively removed by changing thereaction gas to the mixed gas of CF₄ and O₂. (FIG. 2(B)) In the terminalportion a terminal 101 and an insulating film 104 a remained.

Next after removing resist masks 108 and 109, a resist mask is formed bya shadow mask, an insulating film 104 b is formed by selectivelyremoving the insulating film 104 a which covers the pad portion of theterminal portion and the resist mask is removed. (FIG. 2(C)) Further,the resist mask may be formed by screen printing in place of the shadowmask and it may be used as the etching mask.

Next, a second conductive film 116 comprising a transparent conductivefilm is deposited over the entire surface. (FIG. 2(D)) A top view inthis state is shown in FIG. 5. Note however, for simplification, thesecond conductive film 116 deposited over the entire surface is notshown in FIG. 5.

The second conductive film 116 is formed from a material such as indiumoxide (In₂O₃) or indium tin oxide alloy (In₂O₃—SnO₂, abbreviated as ITO)using a method such as sputtering or vacuum evaporation. The etchingprocess for this type of material is performed using a solution ofhydrochloric acid type. However, a residue is easily generated,particularly by ITO etching, and therefore an indium oxide zinc oxidealloy (In₂O₃—ZnO) may be used in order to improve the etchingworkability. The indium oxide zinc oxide alloy has superior surfacesmoothing characteristics, and has superior thermal stability comparedto ITO, and therefore even if the wiring 111 contacting the secondconductive film 116 is made from an Al film, a corrosion reaction can beprevented. Similarly, zinc oxide (ZnO) is also a suitable material, andin addition, in order to increase the transmittivity of visible lightand increase the conductivity, a material such as zinc oxide in whichgallium (Ga) is added (ZnO:Ga) can be used.

Resist masks 117 a to 117 c are formed next by a third photolithographyprocess. Unnecessary portions are then removed by etching, forming afirst amorphous semiconductor film 118, a source region 119, a drainregion 120, the source wiring 121 and the pixel electrode 122, and thesecond conducive films 123 and 124. (FIG. 3(A))

The third photolithography process patterns the second conductive film116, and at the same time removes a part of the wiring 114, the secondamorphous semiconductor film containing an impurity element whichimparts n-type 112 and the first amorphous semiconductor film 110 byetching, forming an opening. In this Embodiment, the second conductivefilm 116 comprising ITO is selectively removed first by wet etchingusing a mixed solution of nitric acid and hydrochloric acid, or a ferricchloride solution, and after removing the wiring 114 by wet etching, apart of the second amorphous semiconductor film 112 containing animpurity element which imparts n-type and the amorphous semiconductorfilm 110 are etched by dry etching. Note that wet etching and dryetching are used in this Embodiment, but the operator may perform onlydry etching by suitably selecting the reaction gas, and the operator mayperform only wet etching by suitably selecting the reaction solution.

Further, the lower portion of the opening reaches the first amorphoussemiconductor film, and the amorphous semiconductor film 118 is formedhaving a concave portion. The wiring 114 is separated into the sourcewiring 121 and the pixel electrode 122 by the opening, and the secondamorphous semiconductor film containing an impurity element whichimparts n-type 112 is separated into the source region 119 and the drainregion 120. Furthermore, the second conductive film 124 contacting thesource wiring covers the source wiring, and during subsequentmanufacturing processes, especially during a rubbing process, fulfills arole of preventing static electricity from developing. Further, as shownin FIG. 9, this second conductive film 124 plays an important role informing connection with FPC in the terminal portion. Also, this secondconductive film 124 plays a role of protecting the source wiring.

Further, a storage capacitor is formed, in this third photolithographyprocess, between the common wiring 103 a and the pixel electrode 122with the insulating film 104 b in the capacitor portion as a dielectric.

In this third photolithography process, the second conductive filmcomprising a transparent conductive film formed in the terminal portionis remained by covering with the resist mask 117 c.

Resist masks 113 a to 113 c are next removed. The cross sectional viewof this state is shown in FIG. 3(B).

Furthermore, FIG. 9(A) shows top views of a gate wiring terminal portion501 and a source wiring terminal portion 502 in this state. Note thatthe same symbols are used for area corresponding to those of FIG. 1 toFIG. 3. Further, FIG. 9(B) corresponds to a cross-sectional view takenalong the lines E-E′ and F-F′ in FIG. 9(A). Reference numeral 503 inFIG. 9(A) comprising a transparent conductive film denotes a connectingelectrode which functions as an input terminal and it enables easyelectrical connection. In addition, in FIG. 9(B) reference numeral 504denotes an insulating film (extended from 104 b), reference numeral 505denotes a first amorphous semiconductor film (extended from 118), andreference numeral 506 denotes a second amorphous semiconductor filmcontaining an impurity element which imparts n-type (extended from 119).

Thus by thus using three photomasks and performing threephotolithography processes, the pixel TFT portion having the reversestagger type n-channel type TFT 201 and the storage capacitor 202 can becompleted. By placing these in a matrix state corresponding to eachpixel and thus composing the pixel portion, one substrate can be made inorder to manufacture an active matrix type electro-optical device. Forconvenience, this type of substrate is referred to as an active matrixsubstrate throughout this specification.

An alignment film 125 is selectively formed next in only the pixelportion of the active matrix substrate. Screen printing may be used as amethod of selectively forming the alignment film 125, and a method ofremoval in which a resist mask is formed using a shadow mask afterapplication of the alignment film may also be used. Normally, apolyimide resin is often used in the alignment film of the liquidcrystal display element. In this Embodiment AL 3046 (manufactured by JSRCorporation) is used as the alignment film.

Next, a rubbing process is then performed on the alignment film 125,orienting the liquid crystal elements so as to possess a certain fixedpre-tilt angle. In case of the IPS method, the preferable pre-tilt angleis approximately 0.5° to 3°, in order to prevent coloring and to obtaingood viewing angle, and in this Embodiment it is set at 1.5°.

After the active matrix substrate and an opposing substrate 127 on whichan alignment film 126 is formed are next joined together by a sealantwhile maintaining a gap between the substrates using spacers, a liquidcrystal material 128 is injected into the space between the activematrix substrate and the opposing substrate. Sphere shaped spacers orcolumnar spacers can be used as the spacers. The number of mask isreduced by one when the columnar spacers are used, and the space betweenthe substrates can be made more uniform and further the process forspraying can be omitted. Note that though not shown in the figure, thereis a region on the opposing substrate, which does not substantiallyfunction as the display region is covered with a black mask here. Aknown n-type liquid crystal or a p-type liquid crystal used in the IPSmethod may be applied to the liquid crystal material 128.

In this Embodiment a p-type liquid crystal material ZLI-4792(manufactured by Merck) in which a pair of substrates are held 3 to 5 μmdistance is preferable, is used in this Embodiment. In case of usingZLI-2806 (manufactured by Merck) is used, a pair of substrates are helda distance of 6 to 8 μm, and the transmitting light and the responsespeed may be optimized. The angle formed between the pixel electrode andthe rubbing direction is preferably set 0.5° to 40° in absolute valuesince a p-type liquid crystal is used, and it is set at 15° in thisEmbodiment. On the other hand, in case of using n-type liquid crystal,the angle formed between the pixel electrode and the rubbing directionwith respect to the axis intersecting perpendicular to the pixelelectrode is set at between 0.5° to 40° in absolute value.

After injecting liquid crystal material next, the opening for injectionis sealed by a resin material.

Next, a flexible printed circuit (FPC) is connected to the inputterminal 101 of the terminal portion. The FPC is formed by a copperwiring 131 on an organic resin film 132 such as polyimide, and isconnected to the transparent conductive film which covers the inputterminal by an anisotropic conductive adhesive. The anisotropicconductive adhesive comprises an adhesive 129 and particles 130, with adiameter of several tens to several hundreds of μm and having aconductive surface plated by a material such as gold, which are mixedtherein. The particles 130 form an electrical connection in this portionby connecting the transparent conductive film on the input terminal 101and the copper wiring 131. In addition, in order to increase themechanical strength of this region, a resin layer 133 is formed. (FIG.3(C))

Note that FIG. 1 is a top view of one pixel and the cross sections takenalong A-A′ line and B-B′ line corresponds respectively to FIG. 3(C). Forsimplification the opposing substrate on which the alignment film isdisposed and the liquid crystal are not shown in the figure.

FIG. 6 is a cross sectional view taken along the chain line X-X′ inFIG. 1. The common wiring 103 a is divided into branches and the portiondivided into branches is referred to as common electrode 103 b and theportion parallel to the gate wiring is referred to as common wiring 103a through the Specification, for convenience. The pixel electrode 122 isdisposed between two common electrodes 103 b. Further, the pixelelectrode 122 and the common electrode 103 b are formed in differentlayers. An electric field is applied by them, between the pixelelectrode 122 and the common electrode 103 b on one substrate, and thedirection is set to be approximately parallel to the substrateinterface.

FIG. 7 is a diagram explaining the arrangement of the pixel section andthe terminal section of an active matrix substrate. A pixel section 211is disposed on the substrate 210, a gate wiring 208 and a source wiring207 are formed to intersect in the pixel section and an n-channel TFT201 is disposed connected to these is disposed corresponding to eachpixel. A pixel electrode 119 and a storage capacitor 202 are connectedto the drain side of the n-channel TFT 201 and the other terminal of thestorage capacitor 202 is connected to the common wiring 209. Thestructures of the n-channel TFT 201 and the storage capacitor 202 arethe same as the n-channel TFT 201 and the storage capacitor 202 shown inFIG. 3(B).

An input terminal section 205 which inputs scanning signal is formed inone edge portion of the substrate and is connected to the gate wiring208 by the connecting wiring 206. Further, an input terminal portion 203which inputs image signal is formed in another edge portion and it isconnected to the source wiring 207 by the connecting wiring 204. Gatewiring 208, source wiring 207 and common wiring 209 are disposed inplural numbers corresponding to the pixel density. It is alsoappropriate to dispose an input terminal 212 which inputs image signalsand the connecting wiring 213, and connect to the source wiringalternately with the input terminal portion 203. The input terminalportions 203, 205 and 212 may be disposed in arbitrary numberrespectively, and it may be properly determined by the operator.

Embodiment 2

FIG. 8 is an example of a method of mounting a liquid crystal displaydevice. The liquid crystal display device has an input terminal portion302 formed in an edge portion of a substrate 301 on which TFTs areformed, and as shown by embodiment 1, this is formed by a terminal 303formed from the same material as a gate wiring. An opposing substrate304 is joined to the substrate 301 by a sealant 305 encapsulatingspacers 306, and in addition, polarizing plates 307 and 308 and a colorfilter (not shown) are disposed. Note that the arrangement of one of thepolarizing plate may be adjusted to the longer axis of the liquidcrystal molecule and the arrangement of the other polarizing plate maybe adjusted to the shorter axis of the liquid crystal molecule. This isthen fixed to a casing 321 by spacers 322.

Note that the TFT obtained in Embodiment 1 having an active layer formedby an amorphous silicon film has a low electric field effect mobility,and only approximately 1 cm²/Vsec is obtained. Therefore, a drivercircuit for performing image display is formed by an IC chip, andmounted by a TAB (tape automated bonding) method or by a COG (chip onglass) method. In this Embodiment, an example is shown of forming thedriver circuit in an IC chip 313, and mounting by using the TAB method.A flexible printed circuit (FPC) is used, and the FPC is formed by acopper wiring 310 on an organic resin film 309, such as polyimide, andis connected to the input terminal 302 by an anisotropic conductiveadhesive. The input terminal is a transparent conductive film formed onand contacting the wiring 303. The anisotropic conductive adhesive isstructured by an adhesive 311 and particles 312, with a diameter ofseveral tens to several hundreds of μm and having a conductive surfaceplated by a material such as gold, which are mixed therein. Theparticles 312 form an electrical connection in this portion byconnecting the input terminal 302 and the copper wiring 310. Inaddition, in order to increase the mechanical strength of this region, aresin layer 318 is formed.

The IC chip 313 is connected to the copper wiring 310 by a bump 314, andis sealed by a resin material 315. The copper wiring 310 is thenconnected to a printed substrate 317 on which other circuits such as asignal processing circuit, an amplifying circuit, and a power supplycircuit are formed, through a connecting terminal 316. A light source319 and a light conductor 320 are formed on the opposing substrate 304and used as a back light in the transmission type liquid crystal displaydevice.

Embodiment 3

In this Embodiment, an example of forming a protecting film is shown inFIG. 14. Note that this Embodiment is identical to Embodiment 1 throughthe state of FIG. 3(B), and therefore only points of difference areexplained. Further, the same symbols are used for locationscorresponding to those in FIG. 3(B).

After first forming through the state of FIG. 3(B) in accordance withEmbodiment 1, a thin inorganic insulating film is formed on the entiresurface. An inorganic insulating film formed by using plasma CVD orsputtering such as a silicon oxide film, a silicon nitride film, asilicon oxynitride film, or a tantalum oxide film is used as the thininorganic insulating film, and a single layer or a lamination structuremade from these materials may be formed.

A forth photolithography process is performed next, forming a resistmask, and unnecessary portions are removed by etching, forming aninsulating film 402 in the pixel TFT portion, and an inorganicinsulating film 401 in the terminal portion. These inorganic insulatingfilms 401 and 402 function as passivation films. Further, the thininorganic insulating film 401 is removed in the terminal portion by thefourth photolithography process, exposing the second conductive filmcomprising a transparent conductive film formed on the terminal 101 ofthe terminal portion.

The reverse stagger type n-channel type TFT and the storage capacitor,protected by the inorganic insulating film, can thus be completed inthis Embodiment by performing the photolithography process using fourphotomasks four times in total. By thus structuring the pixel portion byarranging these into a matrix state corresponding to each pixel, onesubstrate for manufacturing the active matrix electro-optical device canbe made.

Note that it is possible to freely combine the present Embodiment withconstitutions of Embodiment 1 or Embodiment 2.

Embodiment 4

In Embodiment 1 an example centering on laminating an insulating film, afirst amorphous semiconductor film, a second amorphous semiconductorfilm containing an impurity element which imparts n-type conductivity,and a first conductive film by sputtering, but this Embodiment shows anexample of using plasma CVD to form the films.

The insulating film, the first amorphous semiconductor film, and thesecond amorphous semiconductor film containing an impurity element whichimparts n-type conductivity are formed by plasma CVD in this Embodiment.

In this Embodiment, a silicon oxynitride film is used as the insulatingfilm, and formed with a thickness of 150 nm by plasma CVD. Depositionmay be performed at this point in a plasma CVD apparatus with a powersupply frequency of 13 to 70 MHz, preferably between 27 and 60 MHz. Byusing a power supply frequency of 27 to 60 MHz, a dense insulating filmcan be formed, and the voltage resistance can be increased as a gateinsulating film. Further, a silicon oxynitride film manufactured byadding N₂O to SiH₄ and NH₃ has a reduced fixed electric charge densityin the film, and therefore is a material which is preferable for thisuse. Of course, the gate insulating film is not limited to this type ofsilicon oxynitride film, and a single layer or a lamination structureusing other insulating films such as s silicon oxide film, a siliconnitride film, or a tantalum oxide film may be formed. Further, alamination structure of a silicon nitride film in a lower layer, and asilicon oxide film in an upper layer may be used.

For example, when using a silicon oxide film, it can be formed by plasmaCVD using a mixture of tetraethyl orthosilicate (TEOS) and O₂, with thereaction pressure set to 40 Pa, a substrate temperature of 250 to 350°C., and discharge at a high frequency (13.56 MHz) power density of 0.5to 0.8 W/cm². Good characteristics as the gate insulating film can beobtained for the silicon oxide film thus formed by a subsequent thermalanneal at 300 to 400° C.

Typically, a hydrogenated amorphous silicon (a-Si:H) film is formed witha thickness of 100 nm by plasma CVD as the first amorphous semiconductorfilm. At this point, the deposition may be performed with a power supplyfrequency of 13 to 70 MHz, preferably between 27 and 60 MHz, in theplasma CVD apparatus. By using a power frequency of 27 to 60 MHz, itbecomes possible to increase the film deposition speed, and thedeposited film is preferable because it becomes an a-Si film having alow defect density. In addition, it is also possible to apply amicrocrystalline semiconductor film and a compound semiconductor filmhaving an amorphous structure, such as an amorphous silicon germaniumfilm, as the first amorphous semiconductor film.

Further, if 100 to 100 kHz pulse modulation discharge is performed inthe plasma CVD film deposition of the insulating film and the firstamorphous semiconductor film, then particle generation due to the plasmaCVD gas phase reaction can be prevented, and pinhole generation in thefilm deposition can also be prevented, and therefore is preferable.

Further, in this Embodiment a second amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity isformed with a thickness of 20 to 80 nm as a semiconductor filmcontaining a single conductivity type impurity element. For example, ana-Si:H film containing n-type impurity element may be formed, and inorder to do so, phosphine (PH₃) is added at a 0.1 to 5% concentration tosilane (SiH₄). Alternatively, a hydrogenated microcrystalline siliconfilm (pc-Si:H) may also be used as a substitute for the second amorphoussemiconductor film 106 containing an impurity element which impartsn-type conductivity.

These films can be formed in succession by appropriately changing thereaction gas. Further, these films can be laminated successively withoutexposure to the atmosphere at this time by using the same reactionchamber or a plurality of reaction chambers in the plasma CVD apparatus.By thus depositing successively these films without exposing the filmsto the atmosphere, the mixing in of impurities into the first amorphoussemiconductor film can be prevented.

Note that it is possible to combine this Embodiment with any one ofEmbodiments 1 to 3.

Embodiment 5

Examples are shown in Embodiment 1 and Embodiment 4 of laminating aninsulating film, a first amorphous semiconductor film, a secondamorphous semiconductor film containing an impurity element whichimparts n-type, and a first conductive film, in order and in succession.An example of an apparatus prepared with a plurality of chambers, andused for cases of performing this type of successive film deposition isshown in FIG. 10.

An outline as seen from above of an apparatus (successive filmdeposition system), shown by this Embodiment, is shown in FIG. 10.Reference numerals 10 to 15 in FIG. 10 denote chambers having airtightcharacteristics. A vacuum evacuation pump and an inert gas introductionsystem are arranged in each of the chambers.

The chambers denoted by reference numerals 10 and 15 are load-lockchambers for bringing test pieces (processing substrates) 30 into thesystem. The chamber denoted by reference numeral 11 is a first chamberfor deposition of the insulating film 104. The chamber denoted byreference numeral 12 is a second chamber for deposition of the firstamorphous semiconductor film 105. The chamber denoted by referencenumeral 13 is a third chamber for deposition of the second amorphoussemiconductor film 106 which imparts n-type conductivity. The chamberdenoted by reference numeral 14 is a fourth chamber for deposition ofthe first conductive film 107. Further, reference numeral 20 denotes acommon chamber of the test pieces, arranged in common with respect toeach chamber.

An example of operation is shown below.

After pulling a high vacuum state in all of the chambers at first, apurge state (normal pressure) is made by using an inert gas, nitrogenhere. Furthermore, a state of closing all gate valves 22 to 27 is made.

First, a cassette 28 loaded with a multiple number of processingsubstrates is placed into the load-lock chamber 10. After the cassetteis placed inside, a door of the load-lock chamber (not shown in thefigure) is closed. In this state, the gate valve 22 is opened and one ofthe processing substrates 30 is removed from the cassette, and is takenout to the common chamber 20 by a robot arm 21. Position alignment isperformed in the common chamber at this time. Note that a substrate onwhich the wirings 101, 102, 103 a and 103 b are formed, obtained inaccordance with Embodiment 1, is used for the substrate 30.

The gate valve 22 is then closed, and a gate valve 23 is opened next.The processing substrate 30 is then moved into the first chamber 11.Film deposition processing is performed within the first chamber at atemperature of 150 to 300° C., and the insulating film 104 is obtained.Note that a film such as a silicon nitride film, a silicon oxide film, asilicon oxynitride film, or a lamination film of these films, can beused as the insulating film. A single layer silicon nitride film isemployed in this Embodiment, but a two-layer, three-layer, or higherlayer lamination structure film may also be used. Note that a chambercapable of plasma CVD is used here, but a chamber which is capable ofsputtering by use of a target may also be used.

After completing the deposition of the insulating film, the processingsubstrate is pulled out into the common chamber by the robot arm, and isthen transported to the second chamber 12. Film deposition is performedwithin the second chamber at a temperature of 150 to 300° C., similar tothat of the first chamber, and the first amorphous semiconductor film105 is obtained by plasma CVD. Note that a film such as amicrocrystalline semiconductor film, an amorphous germanium film, anamorphous silicon germanium film, or a lamination film of these films,etc., can be used as the first amorphous semiconductor film. Further, aheat treatment process for reducing the concentration of hydrogen may beomitted with a formation temperature of 350 to 500° C. for the firstamorphous semiconductor film. Note that a chamber capable of plasma CVDis used here, but a chamber which is capable of sputtering by use of atarget may also be used.

After completing deposition of the first amorphous semiconductor film,the processing substrate is pulled out into the common chamber and thentransported to the third chamber 13. Film deposition process isperformed within the third chamber at a temperature of 150° C. to 300°C., similar to that of the second chamber, and the second amorphoussemiconductor film 106, containing an impurity element which impartsn-type conductivity (P or As), is obtained by plasma CVD. Note that achamber capable of plasma CVD is used here, but a chamber which iscapable of sputtering by use of a target may also be used.

After completing deposition of the second amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity, theprocessing substrate is pulled out into the common chamber, and then istransported to the fourth chamber 14. The first conductive film 107 isobtained within the fourth chamber by sputtering using a metallictarget.

The processed substrate, on which four layers have thus been formed insuccession, is then transported to the load-lock chamber 15 by the robotarm, and is contained in a cassette 29.

Note that the apparatus shown in FIG. 10 is only one example. Further,it is possible to freely combine this Embodiment with any one ofEmbodiments 1 to 4.

Embodiment 6

In Embodiment 5, an example of successive lamination using a pluralityof chambers is shown, but in this Embodiment a method of successivelamination within one chamber maintained at high vacuum using theapparatus shown in FIG. 11 is employed.

The apparatus system shown in FIG. 11 is used in this Embodiment. InFIG. 11, reference numeral 40 denotes a processing substrate, referencenumeral 50 denotes a common chamber, 44 and 46 denote load-lockchambers, 45 denotes a chamber, and reference numerals 42 and 43 denotecassettes. In order to prevent contamination developing during transportof the substrate, lamination is performed in the same chamber in thisEmbodiment.

It is possible to freely combine this Embodiment with any one ofEmbodiments 1 to 4.

Note however, when applied to Embodiment 1, a plurality of targets areprepared in the chamber 45, and the insulating film 104, the firstamorphous semiconductor film 105, the second amorphous semiconductorfilm 106 containing an impurity element which imparts n-typeconductivity, and the first conductive film 107 may be laminated bychanging the reaction gas in order.

Further, when applied to Embodiment 4, the insulating film 104, thefirst amorphous semiconductor film 105, and the second amorphoussemiconductor film 106 containing an impurity element which impartsn-type conductivity, may be laminated by changing the reaction gas inorder.

Embodiment 7

In Embodiment 1, an example of forming the second amorphoussemiconductor film containing an impurity element which imparts n-typeby using sputtering is shown, but in this Embodiment an example offorming it by using plasma CVD is shown. Note that, except for themethod of forming the second amorphous semiconductor film containing animpurity element which imparts n-type, this Embodiment is identical toEmbodiment 1, and therefore only differing points are stated below.

If phosphine (PH₃) is added at a concentration of 0.1 to 5% with respectto silane (SiH₄) as a reaction gas using plasma CVD, then the secondamorphous semiconductor film containing an impurity element whichimparts n-type can be obtained.

Embodiment 8

In Embodiment 7, an example of forming the second amorphoussemiconductor film containing an impurity element which imparts n-typeby using plasma CVD is shown, and in this Embodiment, an example ofusing a microcrystalline semiconductor film containing an impurityelement which imparts n-type conductivity is shown.

By setting the deposition temperature from 80 to 300° C., preferablybetween 140 and 200° C., taking a gas mixture of silane diluted byhydrogen (SiH₄:H₂=1:10 to 100) and phosphine (PH₃) as the reaction gas,setting the gas pressure from 0.1 to 10 Torr, and setting the dischargepower from 10 to 300 mW/cm², a microcrystalline silicon film can beobtained. Further phosphorous may be added by plasma doping after filmdeposition of this microcrystalline silicon film.

Embodiment 9

FIG. 12 is a diagram which schematically shows a state of constructingan electro-optical display device by using the COG method. A pixelregion 803, an external input-output terminal 804, and a connectionwiring 805 are formed on a first substrate. Regions surrounded by dottedlines denote a region 801 for attaching a scanning line side IC chip,and a region 802 for attaching a data line side IC chip. An opposingelectrode 809 is formed on a second substrate 808, and this is joined tothe first substrate 800 by using a sealing material 810. A liquidcrystal layer 811 is formed inside the sealing material 810 by injectinga liquid crystal. The first substrate and the second substrate arejoined with a predetermined gap, and this is set from 3 to 8• for anematic liquid crystal.

IC chips 806 and 807 have circuit structures which differ between thedata line side and the scanning line side. The IC chips are mounted onthe first substrate. An FPC (flexible printed circuit) 812 is attachedto the external input-output terminal 804 in order to input power supplyand control signals from the outside. In order to increase the adhesionstrength of the FPC 812, a reinforcing plate 813 may be formed. Theelectro-optical device can thus be completed. If an electricalinspection is performed before mounting the IC chips on the firstsubstrate, then the final process yield of the electro-optical devicecan be improved, and the reliability can be increased.

Further, a method such as a method of connection using an anisotropicconductive material or a wire bonding method, can be employed as themethod of mounting the IC chips on the first substrate. FIG. 13 show anexample of such. FIG. 13(A) shows an example in which an IC chip 908 ismounted on a first substrate 901 using an anisotropic conductivematerial. A pixel region 902, a lead wire 906, a connection wiring andan input-output terminal 907 are formed on the first substrate 901. Asecond substrate is bonded to the first substrate 901 by using a sealingmaterial 904, and a liquid crystal layer 905 is formed therebetween.

Further, an FPC 912 is bonded to one edge of the connection wiring andthe input-output terminal 907 by using an anisotropic conductivematerial. The anisotropic conductive material is made from a resin 915and conductive particles 914 having a diameter of several tens toseveral hundreds of μm and plated by a material such as Au, and theconnection wiring 913 formed with the FPC 912 and the connection wiringand input-output terminal 907 are electrically connected by theconductive particles 914. The IC chip 908 is also similarly bonded tothe first substrate by an anisotropic conductive material. Aninput-output terminal 909 provided with the IC chip 908 and the leadwire 906, or a connection wiring and the input-output terminal 907 areelectrically connected by conductive particles 910 mixed into a resin911.

Furthermore, as shown by FIG. 13(B), the IC chip may be fixed to thefirst substrate by an adhesive material 916, and an input-outputterminal of an IC chip and a lead wire or a connection wiring may beconnected by an Au wire 917. Then, this is all sealed by a resin 918.

The method of mounting the IC chip is not limited to the method based onFIGS. 12 and 13, and it is also possible to use a known method notexplained here, such as a COG method, a wire bonding method or a TABmethod.

It is possible to freely combine this Embodiment with Embodiment 1, 3 or8.

Embodiment 10

In the embodiment 1, although the description has been made on theexample in which the transparent conductive film covering the pixelelectrode and the source electrode is formed, in this embodiment, anexample in which a transparent conductive film is not formed will bedescribed by use of FIG. 15.

In accordance with the embodiment 1, the state of FIG. 2(C), that is, agate wiring 602, a common wiring 603 a, a common electrode 603 b, and awiring (which becomes a source wiring and a pixel electrode in asubsequent step) are obtained.

Resist mask is formed next by a third photolithography process.Unnecessary portion is then removed by etching, forming a firstamorphous semiconductor film, a source region, a drain region, thesource wiring 621, and the pixel electrode 622.

The third photolithography process removes the wiring the secondamorphous semiconductor film containing an impurity element whichimparts n-type conductivity and a portion of the first amorphoussemiconductor film by etching, forming an opening. In the embodiment 1,after selectively removing the wiring 111 by wet etching and forming thesource wiring 621 and the pixel electrode 622, the second amorphoussemiconductor film, containing the impurity element which imparts n-typeconductivity, and a portion of the amorphous semiconductor film areetched by dry etching. Note that wet etching and dry etching are used inthe embodiment 1, but the operator may perform only dry etching bysuitably selecting the reaction gas, and the operator may perform onlywet etching by suitably selecting the reaction solution.

Further, the lower portion of the opening reaches the first amorphoussemiconductor film, and the first amorphous semiconductor film is formedhaving a concave portion. The wiring is separated into the source wiring621 and the pixel electrode 622 by the opening, and the second amorphoussemiconductor film, containing an impurity element which imparts n-typeconductivity is separated into the source region and the drain region.

If subsequent steps are performed in accordance with the embodiment 1and fabrication is made, an active matrix substrate is obtained.

It is possible to freely combine the embodiment 6 with any one of theembodiments 1 to 9.

Embodiment 11

The present Embodiment shows an example of using a plastic substrate (ora plastic film) for the substrate. Note that since this Embodiment isalmost identical to Embodiment 1 without the use of plastic substratefor the substrate, only different points are described.

PES (polyethylene sulfone), PC (polycarbonate), PET (polyethyleneterephthalate) and PEN (polyethylene naphthalate) can be used as theplastic substrate material.

An active matrix substrate is completed using the plastic substrateprovided that manufacturing is performed in accordance withEmbodiment 1. Note that it is preferable to form the insulating film,the first amorphous semiconductor film, and the second amorphoussemiconductor film containing an impurity element which imparts n-typeconductivity by sputtering with the relatively low film depositiontemperature.

A TFT having good characteristics can be formed on the plasticsubstrate, and the resulting display device can be made low weight.Further, it is possible to make a flexible electro-optical devicebecause the substrate is plastic. Furthermore, assembly becomes easy.

Note that this Embodiment can be freely combined with any one ofEmbodiments 1 to 3, 9 and 10.

Embodiment 12

In the present embodiment, an example of forming a protecting circuit ina region other than a pixel portion in the same process in which secondconductive films 123 and 124 covering the pixel electrode and sourcewiring can be formed is shown in FIG. 16.

In FIG. 16(A), reference numeral 701 denotes a wiring, and shows a gatewiring, a source wiring, or a common wiring extended from the pixelportion. Further, electrodes 701 are laid down in regions in which thewiring 701 is not formed, and are formed so as not to overlap the wiring701. The present embodiment shows an example of forming the protectingcircuit without increasing the number of masks, but there is no need tolimit the structure to that of FIG. 16(A). For example, the number ofmasks may be increased and then, the protecting circuit may be formed bya protecting diode or a TFT.

Further, FIG. 16(B) shows an equivalent circuit diagram.

By making this type of constitution, the generation of staticelectricity due to friction between production devices and an insulatingsubstrate can be prevented during the production process. In particular,the TFTs etc. can be protected from static electricity developing duringa liquid crystal orienting process of rubbing performed duringmanufacture.

Note that the present embodiment can be freely combined with any one ofthe embodiments 1 to 11.

Embodiment 13

A bottom gate type TFT formed by implementing any one of the aboveembodiments 1 to 12 can be used in various electro-optical devices (suchas an active matrix type liquid crystal display device). Namely, thepresent invention can be implemented in all electronic equipment inwhich these electro-optical devices are built into a display portion.

The following can be given as such electronic equipment: a video camera,a digital camera, a projector (rear type or front type), a head-mounteddisplay (goggle type display), a car navigation system, a car stereo, apersonal computer, and a portable information terminal (such as a mobilecomputer, a portable telephone or an electronic book). Examples of theseare shown in FIGS. 17 and 18.

FIG. 17(A) is a personal computer, and it includes a main body 2001, animage input portion 2002, a display portion 2003, and a keyboard 2004.The present invention can be applied to the display portion 2003.

FIG. 17(B) is a video camera, and it includes a main body 2101, adisplay portion 2102, an audio input portion 2103, operation switches2104, a battery 2105, and an image receiving portion 2106. The presentinvention can be applied to the display portion 2102.

FIG. 17(C) is a mobile computer, and it includes a main body 2201, acamera portion 2202, an image receiving portion 2203, operation switches2204, and a display portion 2205. The present invention can be appliedto the display portion 2205.

FIG. 17(D) is a player that uses a recording medium on which a programis recorded (hereafter referred to as a recording medium), and theplayer includes a main body 2401, a display portion 2402, a speakerportion 2403, a recording medium 2404, and operation switches 2405. Notethat this player uses a recording medium such as a DVD (digitalversatile disk) or a CD, and the appreciation of music, the appreciationof film, game playing and the Internet can be performed. The presentinvention can be applied to the display portion 2402.

FIG. 17(E) is a digital camera, and it includes a main body 2501, adisplay portion 2502, an eyepiece portion 2503, operation switches 2504,and an image receiving portion (not shown in the figure). The presentinvention can be applied to the display portion 2502.

FIG. 18(A) is a portable telephone, and it includes a main body 2901, anaudio output portion 2902, an audio input portion 2903, a displayportion 2904, operation switches 2905, and an antenna 2906. The presentinvention can be applied to the display portion 2904.

FIG. 18(B) is a portable book (electronic book), and it includes a mainbody 3001, display portions 3002 and 3003, a recording medium 3004,operation switches 3005, and an antenna 3006. The present invention canbe applied to the display portions 3002 and 3003.

FIG. 18(C) is a display, and it includes a main body 3101, a supportstand 3102, and a display portion 3103. The present invention can beapplied to the display portion 3103. The display of the presentinvention is advantageous for a large size screen in particular, and isadvantageous for a display equal to or greater than 10 inches(especially equal to or greater than 30 inches) in the opposite angle.

The applicable range of the present invention is thus extremely wide,and it is possible to apply the present invention to electronicequipment in all fields. Further, the electronic equipment of theembodiment 13 can be realized by using a constitution of any combinationof the embodiments 1 to 12.

1. A method of manufacturing a liquid crystal display device comprising:forming a gate wiring over an insulating surface by using a first mask;forming a common electrode over the insulating surface; forming aninsulating film over the gate wiring; forming a first amorphoussemiconductor film over the insulating film; forming a second amorphoussemiconductor film containing an impurity element which imparts n-typeconductivity, over the first amorphous semiconductor film; forming aconductive film over the second amorphous semiconductor film; patterningthe first amorphous semiconductor film, the second amorphoussemiconductor film and the conductive film together by using a secondmask; and removing a portion of the first amorphous semiconductor film,a portion of the second amorphous semiconductor film and a portion ofthe conductive film to form a source region, a drain region, a sourcewiring after patterning the first amorphous semiconductor film, thesecond amorphous semiconductor film and the conductive film; forming atransparent electrode electrically connected to the conductive film;forming an alignment film over the transparent electrode and the commonelectrode; and forming a protecting circuit comprising a same materialas the common electrode when the common electrode is formed, wherein theportion of the second amorphous semiconductor film is between the sourceregion and the drain region, wherein the transparent electrode and thecommon electrode are disposed so that liquid crystal molecules arecontrolled by an electric field produced between the transparentelectrode and the common electrode, wherein the gate wiring is separatedfrom the common electrode, and wherein the transparent electrode and thecommon electrode are overlapped with each other.
 2. The method ofmanufacturing the liquid crystal display device according to claim 1,wherein the insulating film, the first amorphous semiconductor film, andthe second amorphous semiconductor film are formed in succession withoutexposure to an atmosphere.
 3. The method of manufacturing the liquidcrystal display device according to claim 1, wherein the insulatingfilm, the first amorphous semiconductor film, or the second amorphoussemiconductor film is formed by sputtering.
 4. The method ofmanufacturing the liquid crystal display device according to claim 1,wherein the insulating film, the first amorphous semiconductor film, orthe second amorphous semiconductor film is formed by plasma CVD.
 5. Themethod of manufacturing the liquid crystal display device according toclaim 1, wherein the gate wiring is formed from an element selected fromthe group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, and an alloyof the elements.
 6. A method of manufacturing a liquid crystal displaydevice comprising: forming a gate wiring over an insulating surface byusing a first mask; forming a common electrode over the insulatingsurface; forming an insulating film over the gate wiring; forming afirst amorphous semiconductor film over the insulating film; forming asecond amorphous semiconductor film containing an impurity element whichimparts n-type conductivity, over the first amorphous semiconductorfilm; forming a conductive film over the second amorphous semiconductorfilm; patterning the first amorphous semiconductor film, the secondamorphous semiconductor film and the conductive film together by using asecond mask; and removing a portion of the first amorphous semiconductorfilm, a portion of the second amorphous semiconductor film and a portionof the conductive film to form a source region, a drain region, a sourcewiring after patterning the first amorphous semiconductor film, thesecond amorphous semiconductor film and the conductive film; forming atransparent electrode electrically connected to the conductive film;forming an alignment film over the transparent electrode and the commonelectrode; and forming a protecting circuit comprising a same materialas the common electrode when the common electrode is formed, wherein theportion of the second amorphous semiconductor film is between the sourceregion and the drain region, wherein the transparent electrode and thecommon electrode are disposed so that liquid crystal molecules arecontrolled by an electric field produced between the transparentelectrode and the common electrode, wherein the gate wiring is separatedfrom the common electrode, wherein the transparent electrode and thecommon electrode are overlapped with each other, and wherein the firstamorphous semiconductor film and the second amorphous semiconductor filmextends beneath the source wiring.
 7. The method of manufacturing theliquid crystal display device according to claim 6, wherein theinsulating film, the first amorphous semiconductor film, and the secondamorphous semiconductor film are formed in succession without exposureto an atmosphere.
 8. The method of manufacturing the liquid crystaldisplay device according to claim 6, wherein the insulating film, thefirst amorphous semiconductor film, or the second amorphoussemiconductor film is formed by sputtering.
 9. The method ofmanufacturing the liquid crystal display device according to claim 6,wherein the insulating film, the first amorphous semiconductor film, orthe second amorphous semiconductor film is formed by plasma CVD.
 10. Themethod of manufacturing the liquid crystal display device according toclaim 6, wherein the gate wiring is formed from an element selected fromthe group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, and an alloyof the elements.
 11. The method of manufacturing the liquid crystaldisplay device according to claim 6, wherein inside end faces of thefirst amorphous semiconductor film, the second amorphous semiconductorfilm and the conductive film are substantially coincided by removing theportion of the first amorphous semiconductor film, the portion of thesecond amorphous semiconductor film and the portion of the conductivefilm.
 12. The method of manufacturing the liquid crystal display deviceaccording to claim 6, wherein inside end faces of the first amorphoussemiconductor film, the second amorphous semiconductor film and theconductive film are substantially coincided by removing the portion ofthe first amorphous semiconductor film, the portion of the secondamorphous semiconductor film and the portion of the conductive film. 13.The method of manufacturing the liquid crystal display device accordingto claim 6, wherein the common electrode is formed by using the firstmask.
 14. The method of manufacturing the liquid crystal display deviceaccording to claim 6, wherein the common electrode is formed by usingthe first mask.